The present invention relates to a copper alloy, having high strength, the electrical conductivity and the heat resistance are excellent, the machinability and the adhesion of plating are good, and further the deterioration of interfacial strength with the solder is not observed with the lapse of time, and a method of manufacturing the same. The alloy is suitable for use in the lead frame of semiconductor instruments, in particular.
In general, a lead frame used for semiconductor instruments must have the following characteristics.
(1) High mechanical strength and good heat resistance PA1 (2) High thermal dissipation, that is, high thermal conductivity and electrical conductivity PA1 (3) Good bending formability after formed into frame PA1 (4) Good adhesion of plating and good moldability with resin PA1 (5) Good solderbility, in particular, no time-dependent deterioration at bound portion with solder
In following, a description will be made in detail about the lead frame for which the alloy of the invention is used.
Conventionally, for the lead frame used for electronic instruments, 42 alloy (Fe-42 wt % Ni) has been used principally. This alloy exhibits excellent characteristics as shown by a tensile strength of 63 kg/mm.sup.2 and a heat resistance (a temperature at which the strength becomes to 70% of initial strength by heating for 30 minutes) of 670.degree. C., but the electrical conductivity thereof is inferior being as low as about 3% IACS.
Recently, for semiconductor elements, high reliability has been required together with an increase in the integration degree and the miniaturization, and the shape of semiconductor elements are also changing from conventional DIP type IC to chip carrier type and PGA type. For this reason, the lead frame used for semiconductor elements is also made thin and miniaturized and, at the same time, properties superior to those of 42 alloy have been required. Namely, it is necessary to improve strength to prevent the lowering of strength constituent parts due to the thinning, and to improve the electrical conductivity, being the same characteristic as the thermal conductance. It is also necessary to enhance the thermal radiation due to an increase in the integration degree, further, improve heat resistance, improve the plating operativity and adhesion of plating to the surface of the lead frame for the pretreatment of fixing the semiconductor onto the frame and bonding from semiconductor to wiring at the foot portion of the lead frame. It is also necessary to improve the moldability with sealing resin, and additionally no time-dependent deterioration of binding strength with solder in the connection of the frame to substrate must be observed.